The invention relates to a pipe which is made of plastic, metal, or the like and which has an end portion that plugs into the end of another conduit (i.e., a second pipe) to provide a male/female coupling between the pipe and the conduit. More particularly, the invention relates to a pipe having an end portion with a reduced outer diameter and having a transition portion to the end portion.
German Laid-Open Application number 2,102,163 discloses a method of producing plastic pipes which are drawn-in at one pointed end. The drawn-in end is pushed into the interior of the next-following pipe. The prior art pipes are used, for example, as gutter downspouts. The prior art method produces the pipe in a first process step and, in a second process step, the pipe is widened in a calibrator and then cooled. Thereafter, in a third process step, the free end of a cut-off pipe section is heated to approximately the softening temperature and is pushed in this state over a cooled mandrel. The cooled mandrel has a diameter approximately corresponding to the diameter of the drawing mandrel during manufacture of the pipes. By cooling the pipe end, the latter shrinks onto the cooled mandrel and, in this way, the outer diameter of the drawn-in portion is brought to approximately the circumference of the inner diameter of the widened pipe.
The process of shrinking the pipe end has the result that a conical transition portion forms between the drawn-in plug-in end and the widened pipe.
If the gutter downspouts produced in this manner are pushed together, this conical transition portion abuts against the edge of the free end of the next pipe that has been pushed over the coupling region so that the pipes are held together. This is acceptable for gutter downspouts because only the weight of the coupled pipes is supported by the respective contact regions of successive pipe sections. Such pipe couplings are unable to withstand additional stresses because with increasing force, the pipe end serving as the female member of the coupling tends to bulge out and break, so that the established pipe coupling would be destroyed.